Tohatsu 2.5 waterflow issues

[Balthazar]

Hi folks!

I have bought a used Tohatsu MFS 2.5A 4-stroke 2007 and was pretty happy with the overall condition of the engine, very lightly used! When started first time, the waterflow from the cooling system was very strong and permanent. I have changed the oils and the prop, every time testing the engine again. I saw the flow from the pee pipe was becoming less strong each time I was running the engine. Finally, I went on the canal for about 1.5 hour on an inflatable dinghy Intex. The waterflow was less and less strong and finally stopped. Just drops. This caused the engine stopping 3 times, probaly overheated (it was progressively losing the power, and I needed to add the throttle till half to still run it at a very low speed) and having removed the engine cover, to allow it cooling a bit, I went back home.

I've checked the water pump impeller and it looks very fine, no obstruction in the lower unit as well.

So, do anyone have an idea about this issue and how I possibly could deal with?

Many thanks for help.

 

[colbyt]

Re: Tohatsu 2.5 waterflow issues

Looking good and working properly are not the same thing.

In your situation I would figure out a way to force a stream of fresh water up the intake tube to eliminate an obstruction in the water channels of the motor. My 3.5 also has a flush point (connector require) on the bottom of the engine. If the motor passes water freely from either point, I would replace the impeller as chances are it is the original one.

I hope you haven't damaged by the continued running. I would not run it more than a minute or less until it is pumping a good flow.

 

[pvanv]

Re: Tohatsu 2.5 waterflow issues

You are definitely overheating, and may (or may not) have destroyed the power head. The MFS2.5/3.5A is pretty tough, so you may still be OK once you get the cooling system working again.

There is a water plug (for flushing) on the underside of the power head. That requires a fitting (Part # 3GR724060M, $26.25, available from any dealer) to connect it to a garden hose for flushing, which you should do after running in salt or silt.

Install a new water pump kit (Part # 3AB873220M, $23.03, available from any dealer, including several forum members -- even me) (not just the impeller) and see if that restores proper flow.

 

[Sea Rider]

Re: Tohatsu 2.5 waterflow issues

If 2.5 engine was not well or not flushed at all by prior owner, expect some salt formations build up inside all water passages. Buy the water plug Paul recommends, once screwed on lower crankcase, will create a very narrow strong water jet, thst's if having state of the art house water pressure to wipe clean most small salt, debris water path obstructions.

If after replacing a complete impeller kit, the overheating problems has not been solved, remove cylinder head and mechanically clean all water paths, buy a new spark plug & head gasket and torque to factory specs. Take advantage to clean piston head and cylinder head interiors.

Happy Boating

 

[Balthazar]

Re: Tohatsu 2.5 waterflow issues

Hi folks, thanks a lot for your replies!

I decided to do a deep cleaning first and completely removed the engine from the housing unit. Discovered, as supposed a large build of sea salt plus the pee pipe was blocked from inside by some weeds. Cleaned it thoroughly with a wire brush then a jet washer ))))))

Ordered a new housing gear gasket, and when will mount it back, will see if need to change the power gasket.

Thanks again for help, best regards

 

[Balthazar]

Re: Tohatsu 2.5 waterflow issues

Hi folks, thanks a lot for your replies!

I decided to do a deep cleaning first and completely removed the engine from the housing unit. Discovered, as supposed a large build of sea salt plus the pee pipe was blocked from inside by some weeds. Cleaned it thoroughly...

But it did not help!!!!

After all, it still losing the power.
Just 5-10 min idling and the engine starts turning more and more slowly, I have to add throttle just to keep it running! Then it dies. And there is no way to start the engine, drives me mad.

If I let it cool a bit, it starts again, as nothing happened.

Could you suggest anything, folks? Replacing the power gasket, as I was told before?

Thanks for help

 

[colbyt]

Re: Tohatsu 2.5 waterflow issues

I think more than one of us suggested that you install a new impeller. Looks don't count.

If you don't quit over heating this engine it won't matter because you will have killed it.

 

[Balthazar]

Re: Tohatsu 2.5 waterflow issues

The impeller is in a perfect condition, I have checked it first. The water steam is very strong, I have cleaned the cooling circuit.

 

[MattFL]

Re: Tohatsu 2.5 waterflow issues

Thermostat working?